A Tale of Two Fuel Tanks...it's a tankless job

[Wreckclues]

Long story short, the fuel tank on my M813 rotted out, check out my recent post on "What have you done to your 5-Ton"
Pictured are my old and replacement tanks side by side. The dimensions are the same just the fuel pickup points and plate size are different and there are no vent holes.
What model does this replacement come from?
Can I just drill and thread new vents?
Is there an advantage to having the pickup in the far chamber?

 

[NDT]

I do believe your new tank is from a M39A2 series truck with multifuel engine, that has the electric lift pump in the huge hole.

 

[msgjd]

I do believe your new tank is from a M39A2 series truck with multifuel engine, that has the electric lift pump in the huge hole.

yep i concur with that !

 

[msgjd]

View attachment 952950View attachment 952951

"what's supposed to be here?" : i will have to check my wrecker or the m51a2's to be sure, but that flat boss might be for placing the fitting for the line coming over from the transfer pump on certain M39-series-types that have a pony (reserve) tank on the pass side

"what's this?" : i will look tomorrow, i don't recall ever seeing that dimple before

 

[Wreckclues]

Before I modify the M39 tank to vent like an M809, how did the M39 tanks vent?

 

[Guyfang]

If there is a part number on the new tank, you can find out for sure what it goes on.

 

[Wreckclues]

If there is a part number on the new tank, you can find out for sure what it goes on.

Aside from "DO NOT FILL ABOVE THIS LINE TO ALLOW FOR EXPANSION" There's nothing on the tank.
The invoice from Eastern Surplus lists the National Stock Number as 2910-00-409-4016, Part Number 11648586, identified as coming from an M809 series 5 Ton truck.

 

[Guyfang]

Below is the information copied out of TM 9-2320-260-24P-1, Figure 59, Item #1.

1 PAOOO 2910-00-409-4016 19207 11648586 TANK,FUEL,ENGINE 78 GALLON.........
UOC:614,620,621,622,625,626,628,629,637,638

Below is the list of UOC's. Compare the numbers in red to the list below, and you will know what trucks used this fuel tank.

 

[Wreckclues]

Below is the list of UOC's. Compare the numbers in red to the list below, and you will know what trucks used this fuel tank.

Here's the link to the NSN 2910-00-409-4016, Part Number 11648586 fuel tank advertised on Eastern's website.
Aside from the capacity, dimensions, position of the filler hole and fuel gauge sender it looks nothing like the tank I purchased. With that said it was the only 78 gallon tank they still had in stock and I needed a tank even if I have to modify it, but is it a 11648586 tank?

 

[msgjd]

I believe Eastern erred in the tank description/NSN. Yours looks like what's on the M39A1/A2 series of trucks.. Sorry i forgot to peek at the tank inlet/outlet ports on my M62(A2) and the M51A2's .. Hope to remember this tomorrow

I have a 78g tank from an M809-series, though.. It sits unmodified in the bed of a F350 as a long-distance tank.. There is a dent in the exposed side of it, thus not good for a restoration job.. Not sure what we're going to do with the truck yet, but if it sells there is a 50-50 chance the tank isn't going to be sold with it

 

[msgjd]

View attachment 952950

on the left-hand tank (M39A1/A2-series, 78 gallon, OD, 1-each), what you have marked as "fuel return" is actually the inlet port for the feed line coming from passenger-side 55g aux tank fuel transfer pump on my M62(A2) .. The return line, as well as the feed line actually goes to the big round in-tank pump cover which screws down on the big hole in your new tank .. There is no "vent" on them per se.. However, i recall seeing selectable-vent fill caps on some of the A1's and A2's, right or wrong.

These special fill caps were mostly on the gassers, there's a tab underneath that turns 90-degrees one way or the other to vent or not to vent. IIRC, we were supposed to turn the selector to "closed" when fording but we never did any fording except thru tank-trail mud soup which fortunately was never higher than the top of the fuel tanks except for the sorry sods who happened to be in M151's

IIRC without going out to look, it's dark now and i am in very-inappropriate clothing to fight off bears (and cougars except the 2-legged kind), the M809-series tank "vents" are piped to a port in the PT pump and serve as a pressure-equalizer for the entire system, more than being an actual open-air vent ? Mister Cummins Will Wagner, please pipe in on the function of the M809-series "vent" piping .. Also without going out to look, I think the same situation is also on the commercial 855's having a small line between tanks and the PT pump (am not talking about the fuel return line)

 

[Guyfang]

These special fill caps were mostly on the gassers, there's a tab underneath that turns 90-degrees one way or the other to vent or not to vent.

All the larger Gen sets had these fill caps, up until the late 70 (?) or so. But we also, never closed them. And if someone did, it did not take long before we had gen sets that did not pump fuel from the set tank.

 

[Wreckclues]

without going out to look, it's dark now and i am in very-inappropriate clothing to fight off bears (and cougars except the 2-legged kind),

Now I can't get that image out of my mind...thanks JD

 

[Wreckclues]

the M809-series tank "vents" are piped to a port in the PT pump and serve as a pressure-equalizer for the entire system, more than being an actual open-air vent ?

After making more twists and turns crossing port to starboard my line plumbs into this "doohicky" or perhaps it's a "whatsit"?
At least now I have a port to blow air through to clear the line.